﻿// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information
// 
// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to you under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License. You may obtain a copy of the License at
// 
// http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// 

// .NET Compact Framework 1.0 has no support for Environment.GetEnvironmentVariable()
#if !NETCF

using System;
using System.IO;

namespace log4net.Util.PatternStringConverters
{
    /// <summary>
    /// Write an environment variable to the output
    /// </summary>
    /// <remarks>
    /// <para>
    /// Write an environment variable to the output writer.
    /// The value of the <see cref="log4net.Util.PatternConverter.Option"/> determines 
    /// the name of the variable to output.
    /// </para>
    /// </remarks>
    /// <author>Nicko Cadell</author>
    internal sealed class EnvironmentPatternConverter : PatternConverter
    {
        /// <summary>
        /// Write an environment variable to the output
        /// </summary>
        /// <param name="writer">the writer to write to</param>
        /// <param name="state">null, state is not set</param>
        /// <remarks>
        /// <para>
        /// Writes the environment variable to the output <paramref name="writer"/>.
        /// The name of the environment variable to output must be set
        /// using the <see cref="log4net.Util.PatternConverter.Option"/>
        /// property.
        /// </para>
        /// </remarks>
        protected override void Convert(TextWriter writer, object state) 
        {
            try 
            {
                if (this.Option != null && this.Option.Length > 0)
                {
                    // Lookup the environment variable
                    string envValue = Environment.GetEnvironmentVariable(this.Option);

#if NET_2_0 || NETSTANDARD2_0
                    // If we didn't see it for the process, try a user level variable.
                    if (envValue == null)
                    {
                        envValue = Environment.GetEnvironmentVariable(this.Option, EnvironmentVariableTarget.User);
                    }

                    // If we still didn't find it, try a system level one.
                    if (envValue == null)
                    {
                        envValue = Environment.GetEnvironmentVariable(this.Option, EnvironmentVariableTarget.Machine);
                    }
#endif					

                    if (envValue != null && envValue.Length > 0)
                    {
                        writer.Write(envValue);
                    }
                }
            }
            catch(System.Security.SecurityException secEx)
            {
                // This security exception will occur if the caller does not have 
                // unrestricted environment permission. If this occurs the expansion 
                // will be skipped with the following warning message.
                LogLog.Debug(declaringType, "Security exception while trying to expand environment variables. Error Ignored. No Expansion.", secEx);
            }
            catch (Exception ex) 
            {
                LogLog.Error(declaringType, "Error occurred while converting environment variable.", ex);
            }
        }

        /// <summary>
        /// The fully qualified type of the EnvironmentPatternConverter class.
        /// </summary>
        /// <remarks>
        /// Used by the internal logger to record the Type of the
        /// log message.
        /// </remarks>
        private static readonly Type declaringType = typeof(EnvironmentPatternConverter);
    }
}

#endif // !NETCF
